ASRJC 2025 H2 Chem Hydroxy Compounds Notes

2025 JC2 H2 Hydroxy Compounds 2025/ASRJC/Chemistry 1 Anderson Serangoon Junior College JC2 H2 Chemistry HYDROXY COMPOUNDS Contents/Outline 1 Introduction 2 Nomenclature and Structure 3 Physical properties of alcohols and phenols (SDL) 4 Preparation of alcohols - Electrophilic addition - Nucleophilic substitution - Reduction 5 Chemical properties and reactions of alcohols 6 Acidity of alcohols and phenols 7 Chemical properties and reactions of phenols Learning Outcomes Candidates should be able to: (a) recall the chemistry of alcohols, exemplified by ethanol: (i) combustion (ii) nucleophilic substitution to give halogenoalkanes (iii) reaction with sodium (iv) oxidation to carbonyl compounds and carboxylic acids (v) dehydration to alkenes (b) suggest characteristic distinguishing reactions for the different classes of alcohols (primary, secondary and tertiary alcohols), e.g. mild oxidation (c) deduce the presence of a CH 3CH(OH)– group in an alcohol from its reaction with alkaline aqueous iodine to form tri–iodomethane (d) recall the chemistry of phenol, as exemplified by the following reactions: (i) with bases (ii) with sodium (iii) nitration of, and bromination of, the aromatic ring (e) explain the relative acidities of water, phenol and ethanol in aqueous medium (interpret as Bronsted–Lowry acids) References 1. Organic Chemistry (Sixth Edition), McMurry, Brooks/Cole 2. Chemistry for Advanced Level, Cann and Hughes, Murray

2025 JC2 H2 Hydroxy Compounds 2025/ASRJC/Chemistry 2 1 INTRODUCTION Hydroxy compounds are organic compounds containing the functional group –OH. There are two types of hydroxy compounds: Alcohols Phenols –OH group bonded to a saturated C (sp3 hybridised) of an alkyl group –OH group bonded directly to a C (sp2 hybridised) in the benzene ring Examples: Examples: CH3CH2OH ethanol OH phenol CH2OH phenylmethanol H3C OH 4–methylphenol OH cyclohexanol NO2 OHO2N O2N 2,4,6-trinitrophenol 2 NOMENCLATURE AND STRUCTURE • Alcohols are named with the suffix, –ol, added to the corresponding alkane. CH3OH C CH H H O H H H methanol ethanol • A number is used to indicate the position of the –OH group if there is more than one possible position on the parent chain. CH3CH2CH2CH2OH CH3CHCH2CH3 OH CH3 C H OH C OH H CH2CH3 butan–1–ol butan–2–ol penta–2,3–diol

2025 JC2 H2 Hydroxy Compounds 2025/ASRJC/Chemistry 3 • The benzene ring is named as a ‘phenyl’ group when it is considered as a substituent. CH2OH CH2CH2OH CHCH3 OH phenylmethanol 2–phenylethanol 1–phenylethanol • Compounds that have a hydroxyl group directly attached to a benzene ring are called phenols. The carbon bearing the –OH group is numbered 1, other substituents are numbered relative to it. OH CH3 HO Cl OH NO2NO2 2–methylphenol 4–chlorophenol 3,5–dinitrophenol • In cases where there are higher priority substi